nix: replace rust-overlay with fenix

Signed-off-by: Amneesh Singh <natto@weirdnatto.in>

flake.nix

@@ -9,25 +9,28 @@
       inputs.nixpkgs.follows = "nixpkgs";
     };
 
-    rust-overlay = {
-      url = github:oxalica/rust-overlay;
+    fenix = {
+      url = github:nix-community/fenix;
       inputs.nixpkgs.follows = "nixpkgs";
     };
 
     flake-utils.url = github:numtide/flake-utils;
   };
 
-  outputs = inputs@{ self, nixpkgs, crane, rust-overlay, flake-utils }:
+  outputs = inputs@{ self, nixpkgs, crane, fenix, flake-utils }:
     flake-utils.lib.eachDefaultSystem (system:
       let
         pkgs = import nixpkgs {
           inherit system;
-          overlays = [ rust-overlay.overlays.default ];
+          overlays = [ fenix.overlays.default ];
         };
 
         inherit (pkgs) lib;
 
-        toolchain = pkgs.rust-bin.fromRustupToolchainFile ./rust-toolchain.toml;
+        toolchain = pkgs.fenix.fromToolchainFile {
+          file = ./rust-toolchain.toml;
+          sha256 = "sha256-n8LtGbpj/yCUGo0NFJ7FNv9fSdT9oKEUl+EPLg06JdQ=";
+        };
 
         craneLib = (crane.mkLib pkgs).overrideToolchain toolchain;
         src = craneLib.cleanCargoSource (craneLib.path ./.);

src/ast.rs

@@ -12,7 +12,7 @@ pub enum Entity {
     Fn(Fn),
     Class(Class),
     Module(Module),
-    Static(Let)
+    Static(Let),
 }
 
 /// A module just provides an additional scope

src/parser/mod.rs

@@ -14,7 +14,6 @@ use crate::ast::{
 use crate::lexer::{
     Lexer,
     Token,
-    TokenDelimiter,
     TokenKeyword,
     TokenKind,
     TokenSymbol,